DE 198 05 843 A1 discloses a hydraulic unit for a slip-controlled braking system whose accommodating member contains valve accommodating bores in a first and a second valve row for the accommodation of inlet and outlet valves. Spaced from the two valve rows, a third valve row accommodating so-called special valves is arranged in the block-shaped accommodating member. Between the valve rows arranged in pairs and the third valve row, a pump accommodating bore for a pump driving element is provided in the accommodating member. Accommodating bores for two feeding devices extend in parallel to the valve rows and at right angles to the opening direction of the valve accommodating bores into the accommodating member.
The prior art unit is inappropriate for the use in an electrohydraulic braking system, wherein the vehicle operator only expresses a braking request, which is realized by the braking system so-to-speak ‘by-wire’. This is because in systems of this type it is the purpose of the pump to load a high-pressure accumulator that is used for the pressure increase in the wheel brakes. Based on the high-pressure volume to be supplied, a pump is necessary which not only furnishes pressure fluid under high pressure but also a great pressure fluid volume flow at low operating noises.
It is principally known to use pumps with e.g. three feeding devices for loading a pressure fluid accumulator.
Integrating pumps of this type into a principally known accommodating member of a hydraulic unit—compared to conventional pumps—requires larger space. This contradicts the miniaturization requirement.